The proposed research will fabricate, evaluate and develop diamond and hydrogenated carbon fiber microelectrodes for use in the measurement and detection of electroactive neurotransmitters, related metabolites and other bioanalytes. These new, low oxide and chemically stable microelectrodes have the potential to significantly impact in vitro and in vivo neuroelectrochemical measurements because they solve several problems/complications often encountered with common sp2 carbon fiber microelectrodes. These problems/complications exist because of the presence of electroactive and ionizable surface carbon-oxygen functionalities. Boron-doped microcrystalline and nitrogen-incorporated nanocrystalline diamond films conformally deposited on 20-100 micron diameter W and Mo fibers, and hydrogen plasma treated carbon fibers (pitch and pan-based, 10-40 micron diameter) will be the microelectrodes investigated. These electrode materials offer advantages compared to commonly used sp2 carbon electrodes including a lower voltammetric and amperometric background current; no background voltammetnc features associated with electroactive surface carbon-oxygen functionalities; no variations in the response sensitivity for charged solution analytes due to the absence of ionizable carbon-oxygen functionalities; resistance to fouling due to the nonpolar, hydrogen-terminated surface; low limits of detection; and improved response precision and stability.The goals of the research are (i) to prepare and comprehensively characterize the microelectrodes, (ii) to demonstrate their efficacy for the measurement of neurotransmitters, metabolites and bioanalytes, (iii) to verify that the low oxide surfaces solve the problems/complications that exist in fast scan voltammetric measurements when oxygen functionalized electrodes are used, (iv) to develop a detailed understanding of the electrode reaction kinetics and mechanisms at the hydrogen-terminated surfaces and (v) to apply the electrodes in FIA-EC, LC-EC and CE-EC assays with the objective of significantly improving the analytical detection figures of merit.